The present invention relates to a suspension for supporting a magnetic head of a disk unit incorporated in an information processing apparatus, such as a personal computer, and more particularly to an attachment structure for a flexure of the suspension.
FIG. 9 shows a part of a hard disk drive (HDD) 1. A carriage 2 of the HDD 1 can be turned around a shaft 2a by means of a positioning motor 3 such as a voice coil motor. The carriage 2 is composed of a coil portion 5 located near a magnet 4 of the motor 3, arms (actuator arms) 6 fixed to the coil portion 5, suspensions 7 attached individually to the respective distal end portions of the arms 6, magnetic heads 8 on the respective distal end portions of the suspensions 7, etc. Each head 8 can be moved to a desired track (recording surface) of each of disks 9 by driving the carriage 2 by means of the motor 3.
Each head 8 is provided with a slider 10 in a position such that it can face the track of each disk 9, a transducer (not shown) held on the slider 10, etc. When the disk 9 rotates at high speed, the slider 10 is slightly lifted above the surface of the disk 9, whereby an air bearing is formed between the disk 9 and the slider 10.
FIG. 10 shows an example of the conventional suspension 7. The suspension 7 includes a load beam 11 formed of a thin precision plate spring, a flexure 12 formed of a very thin plate spring fixed to the load beam 11 and a base plate 13 fixed to the proximal portion of the load beam 11, etc. The slider 10 is provided on the distal end portion of the flexure 12. The flexure 12 has rather low stiffness such that the attitude of the lifted slider 10 can flexibly change with respect to the disk 9. The load beam 11 and the flexure 12 are fixed to each other by laser welding or the like in a manner such that they are put in layers in the thickness direction.
A dimple 14 is provided on the distal end portion of the load beam 11. Although the dimple 14 is a hemispherical protuberance that projects toward the slider 10, it is called a dimple in the art because it is recessed on the backside of the load beam 11. As the tip of the dimple 14 abuts on the flexure 12, the head 8 can make three-dimensional displacements, such as pitching and rolling around the dimple 14. In some cases, the dimple 14 may be provided on the flexure 12 in place of the load beam 11.
The load beam 11 and the flexure 12 must be accurately positioned before they are fixed to each other. Conventionally, to attain this, reference holes 15 and 16 are formed in the load beam 11 and the flexure 12, respectively. The laser welding or the like is carried out with a jig pin 17 in the holes 15 and 16 and with the load beam 11 and the flexure 12 clamped in the thickness direction between a pad 18 and a presser member 19 of a clamping device, as shown in FIG. 11.
In order to prevent the jig pin 17 from damaging the load beam 11 or the flexure 12 as it is inserted into the reference holes 15 and 16, in the prior art example, clearances C1 and C2 are required between the outer peripheral surface of the pin 17 and the inner peripheral surface of the holes 15 and 16. Possibly, however, these clearances C1 and C2 may cause the reference holes 15 and 16 to be correspondingly dislocated in the crosswise direction with respect to the jig pin 17, as shown in FIG. 12. Thus, the load beam 11 and the flexure 12 may be subjected to a maximum center deviation of (C1+C2)/2.
If the load beam 11 and the flexure 12 are dislocated in this manner, moments that act on the slider 10 are unbalanced. It is known that the flying height characteristic of the head 8 for the disk is greatly influenced by the moments that act on the slider 10. In order to obtain a steady flying height characteristic, therefore, moments in the rolling direction, in particular, are expected to be distributed equally.
The imbalance of the moments in the rolling direction is attributable to the static rolling angle and dislocation of the dimple 14. In the case where the dimple 14 is provided on the flexure 12, as shown in FIG. 13, the center deviation of the flexure 12 with respect to the load beam 11 is regarded directly as a dimple dislocation .DELTA.D. In the case where the dimple 14 is provided on the load beam 11, as shown in FIG. 14, on the other hand, the center deviation between the load beam 11 and the flexure 12 causes a moment deviation .DELTA.M, and therefore, imbalance of moments attributable to the static rolling angle.
In order to obtain the steady flying height characteristic, therefore, the center deviation between the load beam 11 and the flexure 12 must be minimized. In practice, however, the accuracy of assembly of the load beam 11 and the flexure 12 is subject to variation, so that it is hard to obtain the steady flying height characteristic.
If the relative positions of the load beam 11 and the flexure 12 are deviated, moreover, the following problem will be aroused. To meet the demand for downsizing of heads, wired suspensions have recently been put to practical use. Electrode pads of the wired suspensions are located on the flexure. In consequence, dislocation of the flexure with respect to the load beam causes dislocation of the electrode pads, thus hindering the attachment of magnetic heads.